1. Field of the Invention
This invention relates to a composition that contains poly-4-methylpentene-1 as the main component.
2. Description of the Prior Art
As a non-polar, high-melting crystalline polymer, poly-4-methylpentene-1 has excellent mechanical properties not only at normal temperature but at high temperatures as well, and has excellent dielectric properties over a wide range of temperatures and frequencies. Therefore, poly-4-methylpentene-1 is considered a promising material for use in various applications, especially as an electrical insulation material. However, one great disadvantage of this polymer is its poor flexibility, particularly at low temperatures.
Nowadays, there is an increasing need for flame-retardant electrical insulation materials. This need has made it important to develop technology for rendering poly-4-methylpentene-1, which is inflammable, an industrially applicable electrical insulation material. However, as far as the inventors of this invention known, none of the attempts at blending poly-4-methylpentene-1 with a conventional flame retardant to make the polymer flame-retardant have succeeded to date. This is because the low flexibility of the poly-4-methylpentene-1 becomes even lower as a result of the addition of the flame retardant. Due to these problems associated with poly-4-methylpentene-1, it has not yet become commercially available as a covering material for an electrical wire conductor.
U.S. Pat. No. 3,865,897 proposes improving the physical properties of poly-4-methylpentene-1 by blending it with a special polydiorganosiloxane gum. However, the physical properties, especially elongation, of the polymer obtained in this proposed method are not improved as much as needed. Secondly, the polydiorganosiloxane to be used is expensive. Thirdly, the method requires a separate step to achieve the blending.